Maintaining separation of a treated biological sample from the substances used to treat the sample may be desirable. For instance, a great risk exists concerning transmission of pathogenic agents in biological samples. Treatment of biological samples which potentially contain pathogenic agents may pose a risk to individuals performing the treatment. Additionally, during and after treatment, the sample must remain separated from any potentially contaminated portions to avoid recontamination.
Additionally, it may be desirable to separate portions of a biological sample from other portions of the biological sample. In particular, with a biological sample such as seminal fluid, it may be desirable to separate the more motile sperm from the rest of the sample which may include less motile sperm and to maintain that separation to provide a biological sample with a higher concentration of motile sperm. While density gradients may be used to separate substances, creating and maintaining the density gradient may be difficult, with significant opportunities to mix layers prior to and during use. Such opportunities to mix may be undesirable when dealing with potentially contaminated samples, or when a specific concentration of a treated sample is desired.